Search results for: C.J. Lasnier

Items from 1 to 20 out of 90 results

article

DiMES PMI research at DIII-D in support of ITER and beyond

D.L. Rudakov, T. Abrams, R. Ding, H.Y. Guo, more

Fusion Engineering and Design > 2017 > 124 > C > 196-201

An overview of recent Plasma-Material Interactions (PMI) research at the DIII-D tokamak using the Divertor Material Evaluation System (DiMES) is presented. The DiMES manipulator allows for exposure of material samples in the lower divertor of DIII-D under well-diagnosed ITER-relevant plasma conditions. Plasma parameters during the exposures are characterized by an extensive diagnostic suite including...

article

Analysis of edge stability for models of heat flux width

M.A. Makowski, C.J. Lasnier, A.W. Leonard, T.H. Osborne

Nuclear Materials and Energy > 2017 > 12 > Complete > 1010-1014

Detailed measurements of the n_e, T_e, and T_i profiles in the vicinity of the separatrix of ELMing H-mode discharges have been used to examine plasma stability at the extreme edge of the plasma and assess stability dependent models of the heat flux width. The results are strongly contrary to the critical gradient model, which posits that a ballooning instability determines a gradient scale length related...

article

High-Z material erosion and its control in DIII-D carbon divertor

R. Ding, D.L. Rudakov, P.C. Stangeby, W.R. Wampler, more

Nuclear Materials and Energy > 2017 > 12 > Complete > 247-252

As High-Z materials will likely be used as plasma-facing components (PFCs) in future fusion devices, the erosion of high-Z materials is a key issue for high-power, long pulse operation. High-Z material erosion and redeposition have been studied using tungsten and molybdenum coated samples exposed in well-diagnosed DIII-D divertor plasma discharges. By coupling dedicated experiments and modelling using...

article

Mitigation of divertor heat flux by high-frequency ELM pacing with non-fuel pellet injection in DIII-D

A. Bortolon, R. Maingi, D.K. Mansfield, A. Nagy, more

Nuclear Materials and Energy > 2017 > 12 > Complete > 1030-1036

Experiments have been conducted on DIII-D investigating high repetition rate injection of non-fuel pellets as a tool for pacing Edge Localized Modes (ELMs) and mitigating their transient divertor heat loads. Effective ELM pacing was obtained with injection of Li granules in different H-mode scenarios, at frequencies 3–5 times larger than the natural ELM frequency, with subsequent reduction of strike-point...

article

Modification of adhered dust on plasma-facing surfaces due to exposure to ELMy H-mode plasma in DIII-D

I. Bykov, D.L. Rudakov, S. Ratynskaia, P. Tolias, more

Nuclear Materials and Energy > 2017 > 12 > Complete > 379-385

Transient heat load tests have been conducted in the lower divertor of DIII-D using DiMES manipulator in order to study the behavior of dust on tungsten Plasma Facing Components (PFCs) during ELMy H-mode discharges. Samples with pre-adhered, pre-characterized dust have been exposed at the outer strike point (OSP) in a series of discharges with varied intra-(inter-) ELM heat fluxes. We used C dust...

article

Comparison of 2D simulations of detached divertor plasmas with divertor Thomson measurements in the DIII-D tokamak

T.D. Rognlien, A.G. McLean, M.E. Fenstermacher, M. Groth, more

Nuclear Materials and Energy > 2017 > 12 > Complete > 44-50

A modeling study is reported using new 2D data from DIII-D tokamak divertor plasmas and improved 2D transport model that includes large cross-field drifts for the numerically difficult low anomalous transport regime associated with the H-mode. The data set, which spans a range of plasma densities for both forward and reverse toroidal magnetic field (B_t), is provided by divertor Thomson scattering...

article

Results from core-edge experiments in high Power, high performance plasmas on DIII-D

T.W. Petrie, M.E. Fenstermacher, C.T. Holcomb, T.H. Osborne, more

Nuclear Materials and Energy > 2017 > 12 > Complete > 1141-1145

Significant challenges to reducing divertor heat flux in highly powered near-double null divertor (DND) hybrid plasmas, while still maintaining both high performance metrics and low enough density for application of RF heating, are identified. For these DNDs on DIII-D, the scaling of the peak heat flux at the outer target (q_⊥^P) ∝ [P_SOL x I_P] ^0.92 for P_SOL= 8−19MW and I_P= 1.0–1.4MA, and is consistent...

article

Modeling of detachment experiments at DIII-D

J.M. Canik, A.R. Briesemeister, C.J. Lasnier, A.W. Leonard, more

Journal of Nuclear Materials > 2015 > 463 > C > 569-572

Edge fluid–plasma/kinetic–neutral modeling of well-diagnosed DIII-D experiments is performed in order to document in detail how well certain aspects of experimental measurements are reproduced within the model as the transition to detachment is approached. Results indicate, that at high densities near detachment onset, the poloidal temperature profile produced in the simulations agrees well with that...

article

Application of the radiating divertor approach to innovative tokamak divertor concepts

T.W. Petrie, S.L. Allen, M.E. Fenstermacher, R.J. Groebner, more

Journal of Nuclear Materials > 2015 > 463 > C > 1225-1228

We survey the results of recent DIII-D experiments that tested the effectiveness of three innovative tokamak divertor concepts in reducing divertor heat flux while still maintaining acceptable energy confinement under neon/deuterium-based radiating divertor (RD) conditions: (1) magnetically unbalanced high performance double-null divertor (DND) plasmas, (2) high performance double-null “Snowflake”...

article

ELM mitigation with pellet ELM triggering and implications for PFCs and plasma performance in ITER

L.R. Baylor, P.T. Lang, S.L. Allen, S.K. Combs, more

Journal of Nuclear Materials > 2015 > 463 > C > 104-108

The triggering of rapid small edge localized modes (ELMs) by high frequency pellet injection has been proposed as a method to prevent large naturally occurring ELMs that can erode the ITER plasma facing components (PFCs). Deuterium pellet injection has been used to successfully demonstrate the on-demand triggering of edge localized modes (ELMs) at much higher rates and with much smaller intensity...

article

Electron pressure balance in the SOL through the transition to detachment

A.G. McLean, A.W. Leonard, M.A. Makowski, M. Groth, more

Journal of Nuclear Materials > 2015 > 463 > C > 533-536

Upgrades to core and divertor Thomson scattering (DTS) diagnostics at DIII-D have provided measurements of electron pressure profiles in the lower divertor from attached- to fully-detached divertor plasma conditions. Detailed, multistep sequences of discharges with increasing line-averaged density were run at several levels of P_inj. Strike point sweeping allowed 2D divertor characterization using...

article

Recent sheath physics studies on DIII-D

J.G. Watkins, B. Labombard, P.C. Stangeby, C.J. Lasnier, more

Journal of Nuclear Materials > 2015 > 463 > C > 436-439

A study to examine some current issues in the physics of the plasma sheath has been recently carried out in DIII-D low power Ohmic plasmas using both flush and domed Langmuir probes, divertor Thomson scattering (DTS), an infrared camera (IRTV), and a new calorimeter triple probe assembly mounted on the Divertor Materials Evaluation System (DIMES). The sheath power transmission factor was found to...

article

Control of high-Z PFC erosion by local gas injection in DIII-D

D.L. Rudakov, P.C. Stangeby, C.P.C. Wong, A.G. McLean, more

Journal of Nuclear Materials > 2015 > 463 > C > 605-610

Reduced erosion of a high-Z PFC divertor surface was observed in DIII-D with local injection of methane and deuterium gases. Molybdenum-coated silicon samples were exposed in the lower divertor of DIII-D using DiMES under plasma conditions previously shown to cause significant net erosion of Mo. Three exposures with ¹³CH₄ and one exposure with D₂ gas injection about 12cm upstream of the samples located...

article

Radiative snowflake divertor studies in DIII-D

V.A. Soukhanovskii, S.L. Allen, M.E. Fenstermacher, D.N. Hill, more

Journal of Nuclear Materials > 2015 > 463 > C > 1191-1195

Recent DIII-D experiments assessed the snowflake divertor (SF) configuration in a radiative regime in H-mode discharges with D2 seeding. The SF configuration was maintained for many energy confinement times (2–3s) in H-mode discharges (Ip=1.2MA, PNBI=4–5MW, and B×∇B down (favorable direction toward the divertor)), and found to be compatible with high performance operation (H98y2⩾1). The two studied...

article

Dynamic plasma-wall modeling of ELMy H-mode with UEDGE-MB-W

A.Yu. Pigarov, S.I. Krasheninnikov, T.D. Rognlien, C.J. Lasnier, more

Journal of Nuclear Materials > 2015 > 463 > C > 705-708

The results of time-dependent coupled simulations of the boundary plasma and the first wall deuterium inventory in various sequences of many type-I ELMs with UEDGE-MB-W code are presented. The temporal evolution of deuterium inventories of the pedestal plasma and wall and the calculated rates of particle deposition into the wall during ELMs and of wall outgassing between ELMs are compared to the experimental...

article

Heat flux management via advanced magnetic divertor configurations and divertor detachment

E. Kolemen, S.L. Allen, B.D. Bray, M.E. Fenstermacher, more

Journal of Nuclear Materials > 2015 > 463 > C > 1186-1190

The snowflake divertor (SFD) control and detachment control to manage the heat flux at the divertor are successfully demonstrated at DIII-D. Results of the development and implementation of these two heat flux reduction control methods are presented. The SFD control algorithm calculates the position of the two null-points in real-time and controls shaping coil currents to achieve and stabilize various...

article

Power deposition on the DIII-D inner wall limiter

P.C. Stangeby, C.K. Tsui, C.J. Lasnier, J.A. Boedo, more

Journal of Nuclear Materials > 2015 > 463 > C > 389-392

ITER will use the shaped inner column as startup/rampdown limiter. An exploratory experiment was performed in DIII-D using a similarly shaped inner wall limiter, looking for evidence of a short fall-off feature, λ^short, near the last closed flux surface. Measurements were made on the high field side (HFS) using infrared thermography and a Langmuir swing-probe. In some cases clear evidence was found...

article

Models of SOL transport and their relation to scaling of the divertor heat flux width in DIII-D

M.A. Makowski, C.J. Lasnier, A.W. Leonard, T.H. Osborne, more

Journal of Nuclear Materials > 2015 > 463 > C > 55-60

Strong support for the critical pressure gradient model for the heat flux width has been obtained, in that the measured separatrix pressure gradient lies below and scales similarly to the pressure gradient limit obtained from the ideal, infinite-n stability codes, BALOO and 2DX, in all cases that have been examined. Predictions of a heuristic drift model for the heat flux width are also in qualitative...

chapter

Developing snowflake divertor physics basis in the DIII-D, NSTX and NSTX-U tokamaks aimed at the divertor power exhaust solution.

V.A. Soukhanovskii, S.L. Allen, M.E. Fenstermacher, C.J. Lasnier, more

2015 IEEE 26th Symposium on Fusion Engineering (SOFE) > 1 - 8

2015 IEEE 26th Symposium on Fusion Engineering (SOFE)

Experimental results from the National Spherical Torus Experiment (NSTX), a medium-size spherical tokamak with a compact divertor, and DIII-D, a large conventional aspect ratio tokamak, demonstrate that the snowflake (SF) divertor configuration (D.D. Ryutov, Phys. Plasmas, 14, 064502, 2007) may provide a promising solution for mitigating divertor heat loads and target plate erosion compatible with...

article

The scaling of the heat flux width in DIII-D

M.A. Makowski, C.J. Lasnier, A.W. Leonard, D. Elder, more

Journal of Nuclear Materials > 2013 > 438 > Supplement > S208-S211

A cross machine analysis of heat flux profile measurements has produced a particularly simple scaling law for the scrape-off-layer (SOL) width, going as Bp,mpe with e∼−1.0 where B_p _, _mp is the poloidal magnetic field at the outer midplane separatrix. This result is in very good agreement with a model based on drift-induced transport. We are also developing a model that extends the kinetic ballooning...

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Search results for: C.J. Lasnier

DiMES PMI research at DIII-D in support of ITER and beyond

Analysis of edge stability for models of heat flux width

High-Z material erosion and its control in DIII-D carbon divertor

Mitigation of divertor heat flux by high-frequency ELM pacing with non-fuel pellet injection in DIII-D

Modification of adhered dust on plasma-facing surfaces due to exposure to ELMy H-mode plasma in DIII-D

Comparison of 2D simulations of detached divertor plasmas with divertor Thomson measurements in the DIII-D tokamak

Results from core-edge experiments in high Power, high performance plasmas on DIII-D

Modeling of detachment experiments at DIII-D

Application of the radiating divertor approach to innovative tokamak divertor concepts

ELM mitigation with pellet ELM triggering and implications for PFCs and plasma performance in ITER

Electron pressure balance in the SOL through the transition to detachment

Recent sheath physics studies on DIII-D

Control of high-Z PFC erosion by local gas injection in DIII-D

Radiative snowflake divertor studies in DIII-D

Dynamic plasma-wall modeling of ELMy H-mode with UEDGE-MB-W

Heat flux management via advanced magnetic divertor configurations and divertor detachment

Power deposition on the DIII-D inner wall limiter

Models of SOL transport and their relation to scaling of the divertor heat flux width in DIII-D

Developing snowflake divertor physics basis in the DIII-D, NSTX and NSTX-U tokamaks aimed at the divertor power exhaust solution.

The scaling of the heat flux width in DIII-D

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